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Avalanche Advisory for 2014-03-09 06:28:14

  • EXPIRED ON March 10, 2014 @ 6:28 am
    Published on March 9, 2014 @ 6:28 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

The avalanche danger is MODERATE for above treeline areas. Wind and storm slab avalanche danger will increase through the day on all aspects, above the rain/snow level. Near and below treeline areas will host LOW avalanche danger and likely receive rain on snow.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1: Storm Slab

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Up to 1.3 inches of water is expected from our current storm in progress with snow levels near 8,000 to 9,000 feet. Storm snow avalanches will be possible on upper elevation slopes, above the rain/snow level. We could see up to 8-10 inches of new snow with this storm at/near 10,000 feet.


 

Avalanche Problem 2: Wind Slab

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New snow and southwesterly winds from todays storm will create conditions for wind slab avalanches on N, NE, E, SE, S aspects. Ridgetops and bowls on the upper mountain, above the rain/snow level, will be the best areas to find wind slabs. Slabs could be 6" to several feet deep.

Recent Observations

Warm temperatures yesterday created areas of loose wet avalanches in the form of rollerballs and pinwheels on slopes steeper than 35 degrees. Overall however, good snow stability has been found on all aspects of the southern side of the mountain. Below 8,000 feet, lumpy, rain runneled snow with breakable crust in areas dominates due to high snow levels with the past few storms. Above treeline (8,000ft) the snow smooths out considerably and pretty darn good skiing has been enjoyed by folks over the past few days. Concern for avalanche activity in the next 24-48 hours will be rain on snow creating loose wet avalanche conditions below the rain/snow level, and storm/wind slab avalanches on the upper mountain. This danger will increase as the storm progresses today.

Aerial photo of the South side of Mt Shasta, taken by local pilot Troy Bainbridge just a few days ago.

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From 3-8-14

Overall good snow stability was found yesterday during a tour of Casaval Ridge and Avalanche Gulch. Smooth snow above treeline and good skiing conditions have brought many folks up onto the mountain. A handful of skiers descended from Redbanks yesterday. Snow conditions range from firm, frozen crust, wind packed powder, to smooth and creamy! Lower elevation crusts were sometimes breakable by a skier and sometimes not. Weak layers in the snowpack have varied from location to location. Most common has been failures at or near buried crust layers. However, a pit dug on an east facing aspect of Casaval Ridge yesterday yielded a 2-5 cm weak layer of graupel, about 30 - 40 cm deep. Stability tests showed moderate stability within this weak layer and full slope propagation not likely. (CT11-Q2/ECTN22-Q2)

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From 3-7-14

Of note since last week, at least two avalanches occured in Avalanche Gulch. Both were assumed to be naturally triggered. The larger slide started near The Heart and ran down below Lake Helen, splitting the morain. (D2/3, R2.5)

Photo courtesy of Chris Carr, Shasta Mountain Guides. This photo shows the toe/debris of the larger slide that occured sometime on March 2nd or 3rd. Green Butte and Sargents Ridgelines are in background.

The second, smaller slide occured off of Casaval Ridge and slid down into climbers gully in Avalanche Gulch. The slides were thought to be wind and storm slab avalanches, although the larger of the slides appeared to look like a wet slide due to it's gouging of the snowpack. However, due to the high elevation of the start zone, a wet slide is doubted and it was likely just heavy debris.

Photo courtesy of Chris Carr, Shasta Mountain Guides. Wind Slab avalanche off of Casaval Ridge expected to have occured March 3 or 4th. Lake Helen is up and to the right, out of the photo.

Overall, a thick (2-3 inch) rain crust dominates our backcountry snowpack. I was able to wiggle up to 8,500 feet yesterday in the Old Ski Bowl before visibility became nil. Of course when I returned to Bunny Flat the clouds lifted. Below the crust, very moist. greasy snow exists. While this could cause concern for wet slides, below freezing temperatures last night and said crust will keep this problem unlikely today. The primary concern will be for pockets of wind slab avalanches that have formed on the upper mountain near ridgetops and bowls. These will be found above the rain/snow line, greater than 9,000 feet.

Stability test at test pit yesterday at 8,100 feet, southeast aspect, 31 degrees resulted in an ECTN-Q3 and CT11-Q3@120cm from ground.

Photo courtesy of Chris Carr, Shasta Mountain Guides. Powder riding in Avalanche Gulch from this past week.

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While Northgate, Brewer Ck and Clear Ck trailheads are officially closed, the bathrooms are still open with packout bags inside, and one can still access the Mt Shasta Wilderness. However, your summit pass and wilderness permits must be purchased at McCloud or Mt Shasta Ranger Stations. NO DOGS are allowed in the Mt Shasta Wilderness OR Sierra Club Property. Thanks!

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Terrain:  Remember most of the terrain that we like to play on is greater than 30 degrees.  Avalanches are possible on anything steeper than 30 degrees.  Avoid cornices, rock bands, terrain traps and runout zones of avalanche paths.

Weather:  Most of our areas avalanche danger will occur 24-48 hours after a storm. We still can see persistent weak layers from time to time and we always will be sure to let you know about that!  Heed the basic signs: Wind (significant snow transport and depositions), Temperature (rain/snow/rain/snow, which in turn weakens the snowpack), and Precipitation (Snow or rain add weight and stress to the current snowpack).

SnowpackIf snow accumulates, give the snowpack a chance to adjust to the new snow load before you play on or near steep slopes (greater than 30 degrees).  Most direct action avalanches occur within 24-48 hours of recent snowfall.  Watch for obvious signs of snowpack instability such as recent natural avalanche activity, collapsing of the snowpack (often associated with a “whumphing” sound), and shooting cracks. If you see these signs of instability, limit your recreation to lower angle slopes.

Human Factor: Don’t forget to carry and know how to use avalanche rescue gear. You should NOT be skiing or climbing potential avalanche slopes without having beacons, shovels, and probes.  Only one person in a group should be exposed to potential avalanche danger at a time.  Remember, climbing, skiing, and riding down the edge of slopes is safer than being in the center.  Just because another person is on a slope doesn’t mean that it is safe.  Be an individual!  Make your own decisions.  Heed the signs of instability: rapid warming, “whumphing” noises, shooting cracks, snowing an inch an hour or more, rain, roller balls, wind loading, recent avalanche activity.

 


 

    Weather and Current Conditions

    Weather Summary

    In Mt Shasta City this morning at 0500, we have rain falling with a current temperature of 46 F.

    On Mt Shasta (South Side) in the last 24 hours...

    Old Ski Bowl - 7,600 feet. The Old Ski Bowl weather station has received no new snow in the last 24 hours. The current temperature is 33F with a low of 33F and a high of 52F. Total snow depth is 59 inches with no settlement since yesterday.

    Gray Butte - 8,000 feet - The current temperature is 31F. Temps have ranged from a low of 31F to a high 45F.  Winds have averaged 12 mph from the WNW. Gusts hit 28 mph from the WSW.

    Castle Lake and Mt Eddy (West side of I-5)... 

    Castle Lake - 5,600 feet, the current temperature is 35F with a low of 34F and a high of 57F. Castle Lake has received no new snow and has a current snowpack of 3-4 inches with little settlement since yesterday.

    Mt Eddy - 6,500 feet, the current temperature is 34F with a low of 32F and a high of 52F. Mt Eddy has received no new snow and hosts a current snow depth of 21 inches. Winds have averaged 2 mph with gusts to 12 mph, southerly in nature.

    THIS SEASON: Since September 1st , we have received 10.75 inches of water, normal is 32.13 inches, putting us at 33% of normal. For the year of 2014, Mt Shasta has received 7.93 inches of water with normal being 16.25 inches which puts us at 48% of normal. And lastly, for March we sit at 96% of normal, receiving 1.89 inches of water, normal is 1.96 inches.

    WEATHER SYNOPSIS:

    A wet and windy day today. Forecasts expect up to 1.24" of water for Mt Shasta by 10am Monday morning. One of the warmer storms we've had this year...snow levels are between 8,000 and 9,000 feet this morning and will gradually fall throughout the day to as low as 5,500 feet by Monday morning... a little late for consistent snow at all elevations on the mountain.  Steady westerly winds will be associated with this storm and blow 30-40 mph for today and switching to northwest on Monday, 35-45 mph.

    CURRENT CONDITIONS at Bunny Flat (6950 ft)
    0600 temperature: 33
    Max. temperature in the last 24 hours: 52
    Average wind direction during the last 24 hours: WNW
    Average wind speed during the last 24 hours: 12 mi/hr
    Maximum wind gust in the last 24 hours: 28 mi/hr
    New snowfall in the last 24 hours: 0 inches
    Total snow depth: 59 inches

    Two Day Mountain Weather Forecast

    Produced in partnership with the Medford NWS

    For 7000 ft to 9000 ft
      Sunday
    (4 a.m. to 10 p.m.)
    Sunday Night
    (10 p.m. to 4 a.m.)
    Monday
    (4 a.m. to 10 p.m.)
    Weather Rain Rain, then snow showers Snow showers, mostly cloudy, clearing
    Temperature (°F) 41 29 37
    Wind (mi/hr) East / Southeast 10-20 mph East becoming Northwest 10-20 mph North / Northwest 15-25 mph
    Precipitation SWE / Snowfall (in) / .75-1 water / 2-4 / 1-2
    For 9000 ft to 11000 ft
      Sunday Sunday Night Monday
    Weather Snow Snow Snow, mainly before 11am, cloudy and then clearing
    Temperature (°F) 34 21 27
    Wind (mi/hr) Southwest 35-45 mph Southwest 3-5 Northwest 40-50 mph
    Precipitation SWE / Snowfall (in) / 3-5 / 5-9 / 1-2

    Disclaimer

    This advisory does not apply to Ski Areas or Highways and is for the Mt. Shasta, Castle Lake and Mt. Eddy back country. Use this information for guidance only. You may find different conditions in the back country and should travel accordingly. This advisory expires on midnight of the date it was posted unless otherwise noted.